This invention relates to a workpiece inspecting device for inspecting parts (workpieces) with heads, such as screws, nails and rivets, while moving them using a turntable.
There is known a device in which neck portions of workpieces supplied from a feeder are received in notches formed in the outer periphery of a turntable at regular pitches and the workpieces are moved by rotation of the turntable while supporting the heads of the workpieces on the top surface of the table to check the lengths of the workpieces below their neck portions. Such devices have an advantage that a workpiece introducing portion, an inspecting portion, a portion for ejecting defective workpieces and a portion for taking out non-defectives can be arranged along a circular orbit, so that it can be made small.
A conventional inspecting device of this type is shown in FIG. 8. It has a turntable 1 and a guide 2 provided along the outer periphery of the turntable 1. On the outer periphery of the turntable, notches 3 for receiving necks of workpieces are provided at regular pitches. It supports the heads of the workpieces W on the top surface of the outer periphery of the table 1 and moves the workpieces hanging in the air while preventing them from coming out of the notches 3 with the guide 2. At an intermediate portion of the moving path, a light-emitting portion 4 and a light-receiving portion 5 of an optical sensor are provided opposite to each other. When passing there, the length under the neck of each workpiece is inspected. Any workpiece that has been judged defective in this inspection is ejected at an ejecting portion, so that only non-defectives flow to the takeout portion.
With this conventional inspecting device, since inspection is carried out under the table 1, it is impossible to carry out inspection of overall length of the workpieces or projecting inspection from sideways.
Also, for inspection of the length under the neck, the length from the bottom surface of the table to the tip of each workpiece is measured (assuming that the distance from the bottom surface of the table to the optical path A is constant, partial length on the side of the tip of the workpiece may be measured as shown). But with this method, run-out (that is, vertical displacement) of the workpiece supporting surface (top surface of the table at its outer periphery) causes measurement error. This lowers the measuring accuracy.
Further, among the objects to be inspected, tiny workpieces are increasing (in particular, many screws are tiny). With a conventional inspecting device which has a thick table, no proper inspection is possible because the portion under the neck does not protrude from the bottom surface of the table or the protruding length is too short. As measures against this, if the thickness of the table is reduced, the table tends to be strained, so that the run-out of the workpiece supporting surface grows. In this case, too, proper inspection is impossible.
An object of this invention is to make it possible to carry out overall length inspection and projecting inspection of the entire part of workpieces, using a turntable.
According to the present invention, a turntable includes a hanging portion at outer periphery thereof so that the bottom surface of the turntable at the outer peripheral portion is lower than the bottom surface of the turntable at its center. The hanging portion is provided with windows so as to be opposite to notches. A light emitting portion and a light receiving portion of an optical sensor or a light source for illumination and a camera are arranged opposite to each other inside of the hanging portion and outside of the outer periphery of the turntable, respectively, so that the heads of the workpieces are in the inspecting area through the windows.
According to the present invention, the outer peripheral portion of the turntable is formed by an annular thin plate and the thin plate is fixed to the bottom of the hanging portion by a clamping tool. Thus even tiny workpieces can be inspected without trouble.
Preferably, the turntable is mounted to the bottom of a spindle arranged to extend downwardly and an elevator mechanism is provided to move the turntable in a vertical direction, and a driving means for rotating the spindle is provided.
This invention is also applicable to an inspecting device in which workpieces are transported by being placed on the top surface of the outer periphery of the turntable.
In this invention, because a hanging portion is provided at the outer peripheral portion of the turntable and the head of a workpiece can be taken into the inspecting area through the windows formed in the hanging portion, it is possible to carry out overall length inspection and projecting inspection of an entire workpiece.
Heretofore, overall length of the workpieces was inspected with the workpieces handing in the air by a wire. With this arrangement, displacement of workpieces occurs due to shaking of the wire. Thus, if the measuring timing is judged based on the position of workpieces, malfunction tends to occur. With the device according to this invention, since workpieces are supported by the turntable, which is less liable to shake, such malfunction will not occur.
Also, in the overall length inspection, it is possible to ignore run-out of the workpiece supporting surface. Thus it is possible to accurately determine the length below the neck by subtracting the height of the head from the actually measured overall length.
Further, in a conventional device for inspecting the length of the workpieces below the neck, for tiny workpieces of which the portion below the neck does not sufficiently protrude from the bottom surface of the table, it is impossible to carry out confirmation as to whether the workpieces are on the table. But the device of this invention can perform such confirmation based on the existence or nonexistence of the heads.
By forming the outer peripheral portion of the table from a thin plate, it is possible to inspect tiny workpieces without trouble.
If the outer peripheral portion of the table is thinned and is made integral, it is difficult to remove strain. According to this invention, a separate thin plate is fixed by a clamping tool to prevent strain. This suppresses shaking of workpieces while moving, making stable inspection possible.
By providing an elevator mechanism, it is possible to create a working space under the table by raising the turntable. The table is easily exchangeable.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: